RU2707503C1 - Container cover for transportation and storage of spent nuclear fuel of pressurized water nuclear reactor - Google Patents

Abstract

FIELD: nuclear physics and equipment.

SUBSTANCE: invention relates to covers of containers for transportation and temporary storage of fuel assemblies of pressurized water nuclear reactor (PWR). Container cover for transportation and storage of spent PWR nuclear fuel comprises base with steel disks and aluminum disks arranged between steel discs. At the same time in disks there are two rows of holes. Channels are fitted in holes. Cover is made of one section and is equipped with additional vertical elements of disk attachment arranged along circumference between axes of inner and outer rows of holes in discs. Holes and channels are made round so that they can accommodate canisters for spent fuel assemblies. Cover bottom has grooves and hooks. Inner row of holes has two holes, and in outer row there are eight holes.

EFFECT: invention allows to preserve dimensions of existing covers of transport-and-packaging sets of reactors PWR, improve repairability of cover.

4 cl, 2 dwg

Description

The invention relates to container covers for transportation and temporary storage of fuel assemblies of a water-cooled nuclear reactor (WWER).

The closest prior art to the claimed invention is a container case containing a base on which steel disks are mounted in height and heat-releasing disks located between the steel disks, vertical fasteners connecting the steel and heat-releasing disks to the cover section at this, two rows of holes are made in the disks relative to their axis, pipes are installed in the holes, and the racks are located on the outer perimeter of the disks (RF patent No. 2642853, publ. 01.29.2018).

In a well-known case, a central support pipe is welded to the base. Steel and heat sink discs form at least two sections. Each section is made of two steel disks - the upper and lower, connected by vertical fasteners, in this case, uprights. Between the steel discs there are at least five heat sink discs and spacer sleeves made of aluminum alloy.

Said sections are fixed on the base and between each other in height by means of a central support pipe.

Six pipes are placed in the first row relative to the axis of the carrier pipe, and twelve in the second row.

Assembly cover is as follows.

On the base with a welded central carrier pipe, a lower steel disk is mounted on top. Steel racks are screwed into this disk; heat-releasing disks are strung on them through bushings. Hexagonal pipes are installed in the hex holes of the heat sink discs. The entire assembly is covered with an upper steel disk, forming a section of the cover. The pressing of the upper steel disk to the racks of the section is carried out by screwing the steel racks into the lower steel disk of the next section. The process is repeated until the very top section. A protective disk is mounted on top of the upper steel disk, bolted to the uprights of the last section. A head for lifting equipment is mounted on the central support pipe.

The well-known case is used in a transport packaging container (TUK), which is intended for transportation and storage of air-conditioned spent fuel assemblies (SFA) in the amount of 18 pieces. However, in addition to the transportation of conditioned SFAs, there is a need for the transportation of substandard SFAs for VVER reactors.

When transporting non-standard SFAs, the risk of more serious consequences of the accident increases, therefore, the design of the fuel and energy complex should maximize the safety of transportation of damaged assemblies.

The need to create a new TUK for the SFA of VVER reactors of promising types is due to their rigid nuclear, radiation and thermal characteristics. In this connection, the cover of such a TUK for transportation of substandard SFA can be used only after its completion.

It should also be borne in mind that the dimensions of the TUK of VVER-1000/1200 reactors for the Russian Federation are limited by the existing circulation scheme. Therefore, covers with one or another number of SFAs should fit into the transport and packaging sets of the existing scheme. Placing the maximum possible spent nuclear fuel in a case of existing dimensions requires reducing the distance between the SFA.

Given the existing dimensions of TUK when calculating radiation safety, it was found that the largest number of transported substandard SFAs in terms of radiation load on maintenance personnel is 10, and the increased safety requirements for the transportation of substandard SFAs highlight the following main disadvantages of the prototype.

The presence of several sections requires accurate joining of the sections between each other to ensure alignment of the channels (pipes) in order to exclude the possibility of their engagement during movement (loading / unloading) between the sections and mechanical damage.

In addition, the calculations established that the energy release from the SFA in the selected case is distributed unevenly - with a maximum in the center and a minimum on the periphery. Therefore, the use of sections of known design located one above the other does not guarantee uniform heat removal from the SFA throughout the height of the cover.

In connection with the foregoing, the technical problem of the invention is the transportation and storage of the maximum number of substandard SFA reactors of the VVER-1000/1200 type (10 pieces) in a container case that fit into the TUK dimensions, ensuring the safety of transportation, in particular radiation safety, nuclear safety, heat sink from the SFA.

The technical result is the preservation of the dimensions of the existing covers of the transport and packaging sets of VVER reactors during transportation of substandard fuel, ensuring the safety of transportation, in particular radiation, nuclear safety, heat removal from the SFA to the TUK wall, as well as with the improvement of the maintainability of the cover.

The technical result is achieved by the fact that the container cover for transporting and storing spent nuclear fuel of a water-cooled nuclear reactor containing a base on which steel disks are mounted in height and aluminum disks located between steel disks, vertical fasteners connecting to each other steel and aluminum disks in the section of the case, while in the disks relative to their axis two rows of holes are made, channels are installed in the holes, and vertical elements fasteners are located on the outer perimeter of the disks, the cover is made of one section and is equipped with additional vertical disk fasteners located around the circumference between the axes of the inner and outer rows of holes in the disks, the holes and channels are made round with the possibility of placing canisters in them for spent fuel assemblies, In this case, grooves and hooks for pencil cases are made in the base of the case, two holes are made in the inner row of holes, and eight in the outer row.

In addition, the cover section is provided with additional steel disks, while the steel disks are equidistant from the aluminum disks.

In addition, aluminum and steel discs alternate as follows 4-1-4-1-3-1-3-1-3-1-3-1-3-1, starting from the base.

In addition, the vertical disk mounting elements are made in the form of couplers.

The ability to install sealed canisters (known from the prior art) for SFAs in the canal channels will allow for the transport of substandard SFAs into TUKs without the spread of radioactive substances into the environment, which will ensure the safety requirements for the transportation and storage of spent nuclear fuel.

The round shape of the channels, the grooves and the hook for the pencil cases at the base of the case allow you to place the cases in the case.

A cover made of one section will simplify its design, ensure alignment of the openings for the channels, and improve heat dissipation from the SFA due to the uniform distribution of steel and heat dissipating disks along the height.

An additional number of vertical fasteners is a replacement of the central pipe, allowing you to place the optimal number of substandard SFAs with a reduced distance between them, preserving the dimensions of the existing TUKs and providing the required strength characteristics of the cover during operation and in emergency situations.

The implementation of the vertical fastening elements of the disks in the form of couplers will make the cover section more fixed in height due to the vertical compression force.

The invention is illustrated by drawings, where in FIG. 1 shows a case (longitudinal section), in FIG. 2 shows a cover (cross section). The cover is a metal structure consisting of a base (supporting disk) 1, heat-removing aluminum disks 2, intermediate disks 3, channels 4 for sealed canisters, vertical fasteners, in this case, ties 5 and 6.

Base 1 - a welded construction made of corrosion-resistant steel performs the function of the bearing element of the cover. Top base 1 has grooves 7 and hooks 8 for the installation of pencil cases. The hooks 8 can be made, for example, in the form of a mating hole on the key in the pencil case, made in the groove 6 and offset from its center.

The cover can be equipped with additional steel disks 3. Disks 2 and 3 are located equidistant from each other in a certain order, while in the disks 2 and 3 relative to their axis there are two rows of round holes. Two holes are made in the inner row of holes, and eight in the outer row. Channels 4 (pipes) made of boron steel are installed in the holes, and the channels are configured to place sealed canisters with SFA in them. Channels 4 protect the sealed canisters 4 from mechanical damage.

Aluminum discs 2 simultaneously solve security problems and perform the functions of heat removal from the SFA. Disks intermediate 3 are made of corrosion-resistant steel.

Between 3 steel discs and aluminum discs. 2, bushings 9 of aluminum alloy are installed. The connection of all parts of the cover into a single section is ensured by ties 5 and 6 located along the perimeter of the disks 2 and 3, as well as around the circumference between the axes of the inner and outer rows of holes.

Ties 5, 6 are a stud, the lower end of which is screwed into the support disk 1, and the upper one is fixed with a nut 10.

Assembly cover is as follows.

The support disk 1 is screwed into the supporting element of the cover 1; the screeds 5 and 6 are screwed on. Then, bushings 9, disks 2 and 3 are installed on the screeds 5 and 6, and bushes 9 are also installed between the disks 2 of the cover and the intermediate disks 3. the following: 4-1-4-1-3-1-3-1-3-1-3-1 starting from the reference disk 1. This arrangement of the disks provides the best heat sink from the SFA. Then, channels 4 for leakproof cases in the amount of 10 pcs are passed into the holes of the disks 2 and 3. Then, sleeves 9 are installed on the screeds 5.6 and the last steel disk, the whole structure is fixed with nuts 10, forming a section of the cover.

The operations of loading / unloading canisters sealed into the case are as follows.

Using a reloading machine and a special grip, a sealed pencil case with a substandard SFA is guided and lowered into the channel 4 of the cover until it stops. In this case, the latch on the bottom of the pencil case (key) must fall into the hole 8 on the bottom of the base 1, which ensures that the pencil does not rotate around the axis during transportation and when handling the reloading machine. Next, the grip and pencil case are unhooked. Alternately, all other pencil cases are loaded into the cells of the case. Sealed canisters are unloaded in the reverse order.

The ability to install sealed canisters for SFAs in channels 4 of the case allows for the transport of substandard SFAs into the TUK without the spread of radioactive substances into the environment, which ensures the safety requirements for the transportation and storage of spent nuclear fuel.

The round shape of the channels, the grooves 7 and the hook 8 for the pencil cases at the base of the case allow you to place the cases in the case and prevent them from being damaged during operation.

The cover, made of one single section, simplifies its design, ensures alignment of the holes for channels 4, and improves heat dissipation from the SFA due to the uniform distribution of steel and heat disks along the height.

An additional row of couplers 6 is a replacement of the central pipe, allowing you to place the optimal number of substandard SFAs with a reduced distance between them, preserving the dimensions of the existing TUKs and providing the required strength characteristics of the cover during operation and in emergency situations.

Thus, the proposed TUK provides transportation and storage of the optimal number of substandard SFA reactors of the VVER-1000/1200 type (10 pieces) in a container cover that fits into the dimensions of the existing TUKs, ensuring transportation safety parameters, in particular radiation safety, nuclear safety and heat removal from SFA.

Claims (4)

1. A container case for transporting and storing spent nuclear fuel of a water-cooled nuclear reactor, comprising a base on which steel disks are mounted in height and aluminum disks are arranged between the steel disks, vertical fasteners connecting the steel and aluminum disks in the section of the case, while in the disks relative to their axis two rows of holes are made, channels are installed in the holes, and the vertical fastening elements are located on the outer perimeter disk drive, characterized in that the cover is made of one section and is equipped with additional vertical disk mount elements located around the circumference between the axes of the inner and outer rows of holes in the disks, holes and channels are made round with the possibility of placing canisters in them for spent fuel assemblies, In this case, grooves and hooks for pencil cases are made in the base of the case, two holes are made in the inner row of holes, and eight in the outer row. 2. The case according to claim 1, characterized in that the section of the case is provided with additional steel disks, while the steel disks are equidistant from the aluminum disks. 3. The case according to claim 2, characterized in that the aluminum and steel disks alternate as follows 4-1-4-1-3-1-3-1-3-1-3-1, starting from the base. 4. A case according to claim 1, characterized in that the vertical fastening elements of the disks are made in the form of couplers.

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